50) Ethyl chloride (CHsCI), a substance used as a topical anesthetic, is prepare

Question

50) Ethyl chloride (CHsCI), a substance used as a topical anesthetic, is prepared by reaction of ethylene with hydrogen chloride: Cl(g) HCg)CHsClg 72.3 kJ/mol If 89.5 g of ethylene and 125.0 g of HCl are allowed to react at atmospheric pressure and the volume change is 71.5 L. (negative 71.5 liters), how much PV work is done in kilojoules, and what is the value of AU (change in internal energy) in kilojoules? 51) A piece of 160 g unknown metal is heated to 99.6 °C. Immediately, this unknown metal is placed in of the metal. (Hint: specific heat of water is 4.18 Jg C) g of water at 22.1 C. The system, containing the unknown metal and water, reaches a final temperature at 31.6 oC. Assume that heat is transferred only between the unknown metal and the water. Calculate the specific heat 52) When 1.50 g of magnesium metal is allowed to react with 200 mL of 6.00 M aqueous HCl, the temperature rises from 25 °C to 42.9 °C Mg (s) + 2HCI (a) MgCl(aq)+ H:() Calculate AHrn in kJ/mol for the reaction. Assuming that the heat capacity of the calorimeter is 776 JPC, that the specific heat of the final solution is the same as that of water (4.18 J/g C), and that the density of the solution is 1.00 g/mL. 53) The so-called hydrogen economy is based on hydrogen produced from water using solar energy. Consider the reaction H2O(g) 2H2(g) + Oz(g) 4Hrin +483.6 kl/mol = 2.50 moles of H:0g) are converted to H:(g) and O-(g) against a pressure of 1.00 atm at 25.0°C. Assume the reaction goes to completion. (a) Calculate the work (w) done by this reaction. (b) what is the change in internal energy (AU) for this reaction? Assume the reaction goes to completion. 54) Consider the reaction H2(g) + Cla(g) 2HCl(g) AH-184.6 kJ/mol If 3 moles of H2 react with 3 moles of Clh to form HCI, calculate the work done (in joules) against a pressure of 1.0 atm at 25°C, what is U for this reaction? Assume the reaction goes to completion. 55) Ethyl chloride (CaHsCI), a substance used as a topical anesthetic, is prepared by reaction of ethylene with hydrogen chloride: Ch 4(g) + HCI(g)--"> CthCI(g) /lorn-72.3 kJmol If 89.5 g of ethylene and 125.0 g of HCI are allowed to react at atmospheric pressure and the volume change is 71.5 L (negative 71.5 liters), how much PV work is done in kilojoules, and what is the value of AU (change in internal energy) in kilojoules?

Explanation / Answer

Ans 50

Part a

Work done

W = -PV
= -PV
= -(101.325 kPa)(- 71.5/1000)m³ = 7.25 kJ

Moles of ethylene consumed

= moles of C2H5Cl formed = mass/molecular weight

= 89.5/(12x2+1x5+35.5) = 1.387 moles

Moles of HCl = 125/(1+35.5) = 3.425 moles

E = work/moles formed

= 7.25/1.387 = 5.227 kJ/mol

Since volume contracts,
Energy of the system increases

w>0

U>0
From the enthalpy change
H=U +P (V)

-72.3 kJ = U - 5.227

U = -67.073 kJ

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